The field of orthopedic medicine has grown tremendously in the past fifty years as surgical techniques, implants and instrumentation have developed and been improved. The small bones are frequently subject to the need for re-constructive surgery for example, as a result of trauma, to counteract the effects of aging or to repair congenital deformities and trauma and spinal areas. While there is a wide variety in the exact shape and mass of all bones, these variations become more problematic in providing orthopedic implants for small bone applications since there is less room on and about the bone for the surgeon to place and fix the construct. These bones are finer and have less surface area for placement of an implant, have less mass for the placement of screws and are often surrounded by less muscle and by more vulnerable tendons, blood vessels and nerves. As a result, individual variations become more problematic for orthopedic plates of stock design. Consequently, surgeons have tended to rely on the use of screws and wires for reconstruction or have had to resort to operating room contouring procedures which can weaken the plates and/or distort the screw holes within the plates. This is a particular problem in instances in which either variable locking mechanisms are used, or in which locking screws are used with the plates. None-the-less, locking screws often are used to advantage as they provide more secure placement of the screws in the bone, cause better compression through a fractures, and are less likely to harm the bone or back out of the plate.
One problem that needs to be avoided in the delicate environment of the small bone area is the interference of screws, with other screws, and with the function of ligaments and tendons. While it may be desirable to design an orthopedic plate so that securing screws converge in order to cause compression or increase the pullout strength, it is difficult when a screw impinges on or conflicts with the desired placement of another screw. Some surgeons prefer bicortical fixation in which a screw is sized so that the distil end is secured in cortical bone giving the screw better purchase, however, other surgeons may prefer to avoid placing a screw so that it projects beyond the outer surface of the anchoring bone. These factors are complicated by the relative lack of soft tissue and the presence of ligaments and tendons in the small bone areas. Consequently, the less forgiving biological environment in which the small bone surgeon works requires greater procedural precision and calls for specialized implants and tools.
The present invention is designed to meet the specific needs of the small bone surgeon to facilitate effective and repeatable procedures which provide for ease of use and a range of function for this specific area of specialization. The present invention is specifically intended to provide for the treatment of fracture repair following trauma in an otherwise healthy individual where plates are used to maintain the integrity of the bones while they heal, although it is certainly possible that they may also be used for other surgeries such as reconstruction to correct congenital or age related deformation or issues that relate to prior mal-union of the bone following a prior injury.
The plates of the present invention are designed specifically for the repair or reconstruction of a clavicle, which is commonly called a “collarbone”. The collarbones, like the cheekbones, are covered only by skin, and thus have a high correlation to the appearance of the individuals and serve in many cultures as a marker of beauty. These bones further serve to protect the brachial plexus and the medial nerve and blood vessels that are immediately internal to them. They also serve as a strut and the only skeletal connection between the arms and the torso, and they play a very sophisticated role in the functioning of the shoulder girdle, torso, scapular and arm kinesiology. The effect of misalignment and mal-union of clavicle fractures are only recently being examined from the viewpoint of the strength and stamina of the patient as it was previously viewed radiographically and therefore underestimated.
It has been reported that as many as 5% of all fractures seen in the admissions department of an emergency room are clavicle fractures, which occur most commonly between the proximal ⅔ and the distal ⅓ of the bone. The more common fracture (approximately 80% of clavicle fractures) occurs in the middle third of the clavicle with an upward displacement of the proximal fragment of the bone by the sternocleidomastoid muscle. The weight of the shoulder muscles and of the adductor muscles of the arm may add to the fragment displacement, causing the shoulder to droop. This type of fracture often occurs as a result of a fall on an outstretched hand or of a direct blow to the clavicle. The second most common fracture (which may account for 10-15% of clavicle fractures) occurs in the distal ⅓ of the clavicle. The causes of the fractures are similar to those for the mid-shaft fractures, but also commonly include blows to the shoulder region, such as occur in automobile collisions and particularly physical sports such as hockey, lacrosse and football. Medial fractures are often associated with very severe trauma that includes injury to the vital organs and other indications of co-morbidity.
It is often difficult to reduce and subsequently to maintain the reduction of clavicle fractures without surgical intervention, although both union and healing proceeds rapidly, usually with the result of a prominent callus, and in some cases of mal-union, with the possibility of medial cord nerve symptoms. In the past, non-surgical treatment has often involved immobilization of the associated limb, such as in a figure-of-eight bandage or a simple sling. In a study published in the Journal of Bone and Joint Surgery, 2006 (88:35-40), by McKee et al, Deficits Following Non-operative Treatment of Displaced Mid-shaft Clavicle Fractures, the authors in particular note that that there was a substantial loss of strength and endurance in clavicle fractures treated with a traditional sling approach, indicating substantial residual disability despite apparently adequate range of motion. This and other studies have led to increased concern about providing wider range of surgical options for internal stabilization of the clavicle. However, the problem remains that the shape and size of clavicles vary greatly and their visibility leaves little room for plates that do not generally accommodate this variation gracefully.
The present invention provides answers to the prior art issues by providing a variety of plates with varying footprints that share an elongate central trunk with a medial line (which is intended in this instance to include a curving line) that divides the plate in half laterally. The plate further has at least one pair of terminal asymmetrical arms that extend from the trunk at differing angles relative to the medial line and have differing lengths. The plates also have varying profiles (or contouring) in the z direction but again share a transverse curve along the medial line about the side which faces the bone. The plates also all exhibit bilateral asymmetry (meaning that the left half of the plate is not exactly the same as the right half of plate taken from the medial line) and they all achieve bi-planar screw fixation (meaning that the screws do not lie in a single plane). In addition, while the plates are pre-contoured, the plates are designed to facilitate three dimensional contouring (at least in the terminal arms) to accommodate individual variation in bone shape. The plates are configured to bend laterally, longitudinally, and to wrap or spiral about the longitudinal axis or medial line so that they can be molded to an optimal shape for small bone procedures. The plates are designed to provide optimal stabilization of fractures and osteotomies by providing multi-planar fixation that allows for better pull-out and limited axial loading to the bone. The plates are further designed to accelerate fusion success by reducing or eliminating torsional or twisting stresses to the bone segments during the healing process. In addition, when desired, the plates can be shaped so as to apply a compressive, or even a tensile, force, for example, along the longitudinal axis of a bone.
These plates are provided in a number of variations in a surgical tray, which include for example various lengths of the central trunk portion, which is provided with a line of screw holes centered along the medial line. Further the number of screw holes in the trunk can vary, and the type of holes can vary to include translation slots, compression slots, and locking and non-locking screw holes. Thus, the tray selection allows the surgeon to select his plate during surgery after opening the wound area and considering the plating needs. In addition, the tray includes plates of differing types for differing placement on the clavicles. In a first embodiment of the clavicle plate of the present invention, a plate is provided for placement on the superior aspect of a clavicle, and in a second embodiment, a plate is provided for placement on the anterior/inferior aspect of a clavicle, and in a third embodiment, a plate is provided for placement on the lateral aspect of a clavicle.
All of the plates have an elongate central trunk portion including one or more screw holes which are optionally separated by a waist shaped linking portion along a longitudinal axis or the medial line and depending on the embodiment, the plate has one pair or two pairs of arms which are preferably terminal to the central trunk, and which include screw holes (i.e. one per arm) placed at an equal distance from the longitudinal axis but which diverge asymmetrically from the longitudinal axis to avoid conflicts in the screw placement of the paired arm, specifically, so that the screws of a set of arms avoid impinging on each other and further to provide multiplanar fixation at the plate terminus. The plate is curved about the inferior surface, (i.e. the surface which faces toward and which may, but does not have to fully contact the bone), with a curvature corresponding generally to the curvature of a bony surface. In most of the embodiments of the plate this contouring is the result of a blending of one or more series of radiuses so that the plate may comprise a portion of a cylinder, or portions of a cylinders, or in the event that the medial line also defines a longitudinal curve in the z axis, a portion of a torroid. The pair of arms continue this curvature to spiral or wrap around the bone like a small portion of a double helix (i.e. extending through an arc of less than about 50°). The screw holes within the arms are placed so that the angle of the longitudinal axis of the screws converge in the direction of the distil end of the screw. The screw holes are placed with the longitudinal axis perpendicular to a tangent to the top surface of the arm with the effect that the longitudinal axes of the screws converge in the direction of the distil end. The convergence of the screw holes increases the pull-out strength of the screws.
Further the screw holes are rounded and the corresponding mating heads of the screws are rounded and have a low profile so that the screws can be seated with their longitudinal axes at a variety of angles. Preferably, there is at least 20° of conical rotation, and more preferably 25°, and most preferably 30° of conical rotation of the screw axis in relation to the longitudinal axis of the screw hole (i.e. the longitudinal axis of the screw can be rotated through a conical shape about the axis of the screw hole where the apex of the cone describes an angle of 30°). Alternatively and in many cases, preferably, the screw holes can include internal threads which mate with external threads on the head of the screws to cause locking of the screws relative to the plate.
While the screws are at convergent angles, the screws typically do not in fact impinge on each other, or conflict in their placement since each of the arms of the plate in a pair form a different angle to the central trunk so that the longitudinal axis of the screws are offset from each other along the length of the plate. The radiused configuration of the plate is designed to increase operating room efficiency by facilitating commonly desirable shapes while maintaining the required strength and by permitting bending without deforming the screw holes. This results in making customization in anticipation or during surgery easier.
The surgical tray of the present invention further includes a variety of screws. The screws useful with the plate of the present invention are self-starting, self-tapping screws including the option of partial or full cannulation. The screws include a unique cutting end having multiple flutes, and preferably 2 or 3 flutes about a conical recess. The screws further include a partial taper of the inner diameter in the proximal end over the first several thread turns, for example over 2-8, and preferably over 3-5 turns in order to increase the fatigue life of the screw as well as providing potential physiological advantages in use. The screws further include a torque driving recess that may be a hexagon, a torx shape, or a modification of a torx shape, i.e. a multilobe shape having from 3 to 12 lobes, and preferably having 4 to 8 rounded recesses or lobes. The recess can be of a constant size in the direction of the longitudinal axis, or can taper inward along the longitudinal axis of the screw toward the bottom of the recess. The screws have a low profile, head which is rounded at the junction of the head and the shaft, and also rounded from the maximum diameter toward the top surface or the proximal end relative to the insertion tip, which includes the torque driving recess. This rounded low profile head keeps the screw from having any sharp projecting edges which could provide an irritation to the tissue in the vicinity of the plate and further seats in the plate so that no more than 10% by volume of the screw head projects from the plate.
The instruments for use with the system are well-balanced and ergonomically designed with sufficiently long handles to place the surgeon's hands outside of the line of radiation and designed to reduce fatigue in the operating room.
Depending on the intended placement of the plate, the central trunk, and the plate itself includes a general topography (i.e. the contour in the z direction) designed to maximize the fit on a variety of shapes and sizes of clavicle while enabling, but reducing the need for individualized contouring. This topography includes a c-shape lateral curve in the superior and 4-hole anterior plates, a fishtail (i.e. having a broad curve in the direction of the bone-facing surface of the plate terminating in a short up-turned curve at the end of the plate) shape in the longer anterior plates. The lateral plate has an S-curve of the medial line in the direction of the width of the plate. The plate system of the present invention is thus designed to fit a range of needs of the surgeon operating on the clavicles to allow him or her to perfect a variety of techniques using a set of instruments and a customizable plate and screw construct.